Abstract Laser powder bed fusion (LPBF) is an attractive additive manufacturing technology for preparing high-performance high-entropy alloys (HEAs) engineering components. Unfortunately, the exist of inherent thermal residual stress and non-equilibrium microstructures in the additively manufactured components results in unsatisfactory mechanical properties. Herein, we propose a novel strengthening strategy, namely deep cryogenic treatment (DCT) followed by laser shock peening (LSP), for tailoring the microstructures and performances of a LPBF additively manufactured metastable HEA. The post-treatment effects of DCT+LSP on the LPBF-fabricated Fe50Mn30Co10Cr10 HEA were evaluated in terms of microstructural modifications, residual stress and microhardness redistribution, as well as tensile properties. Results indicate that a gradient heterogeneous structure is formed on the as-built sample surface, featuring gradient variations in grain size, martensitic phase content and dislocation density, due to the grain refinement and martensitic phase transformation under DCT+LSP. The initial tensile residual stress on the surface is completely transformed into compressive stress, reaching a maximum of -289 MPa, and the peak value of microhardness on the surface is improved to 380.8HV. The various strengthening mechanisms of gradient heterogeneous structures, as well as the multiple effects of hetero-deformation induced (HDI) hardening, transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP), are responsible for achieving strength-ductility synergy. This work provides a practical pathway and valuable scientific insights for enhancing mechanical behaviors of additively manufactured metastable HEAs via microstructural engineering.
Tong et al. (2025) studied this question.